Door locks for passenger transit vehicles are a major operational concern inasmuch as they must provide fail-proof locking of the doors in the event of a door mechanism failure to prevent unintentional opening movement of such doors which would permit a passenger to fall out of the vehicle when it is in motion. Yet they must allow for normal door movement upon receipt of the legal open command. It is well known that powered door locks used in the passenger transit door systems utilize a continuous duty independent lock actuator, generally of an electrical, pneumatic, or hydraulic type, engaging a locking member either directly or through an additional linkage to move the locking member into an unlock position. Such locking member generally engages a locking linkage connected to at least one door or a door hanger of a passenger transit vehicle. Such at least one door being in the fully closed and locked position.
Generally, the door is connected to a powered door operator having a prime mover for moving such at least one door in the opening or closing direction. It can be seen from the above discussion that there is a need to enable an independent lock actuator prior to enabling the primary prime mover disposed within a door operator in order to move the at least one door in the opening direction.
Furthermore, the locking member must be maintained in the unlock position for -a predetermined amount of time to allow predetermined movement of at least one door in the opening direction and, more particularly, to allow for the locking linkage connected to at least one door to move in the opening direction to clear the locking member and to allow for removal of power to the independent lock actuator.
Generally, a typical passenger transit vehicle includes at least two to as many as twenty four door systems having a powered lock mechanism and sharing one power source. The requirement to enable the independent lock actuator in working cooperation with a primary mover disposed within a door operator increases power consumption and, more particularly, increases the installation and operating costs to provide such increased power consumption for every door opening movement. Thus, it can be seen from the above discussion that there is a need to reduce power consumption during the unlocking phase of the door movement in the opening direction.
Normally, electrical door systems utilize continuous duty type solenoid lock actuators to minimize power consumption during the unlocking motion. These type of solenoid lock actuators are susceptible to frictional forces and misalignment of the lock mechanism due to vibration or other factors and may result in unreliable operation. Therefore, it is desirable to utilize a more powerful, non-continuous duty type solenoid lock actuator to improve reliability of the door unlocking.
To compensate for design and installation tolerances of the door system components typical unlocking mechanisms include a variety of adjustments to compensate for such tolerances. The unlocking situation is exacerbated by the fact that certain permitted lateral movement of the doors in the closed and locked position exists due to overall system tolerances as well as preload between door edges typically used within door systems. Therefore the adjustments are performed after installation of all door system components and usually require several iterations to assure proper operation. Substantial reduction in the need for adjustment further reduces door system installation costs and increases assembly throughput of the passenger transit vehicle.
For reasons of allowing emergency passenger egress when a power source may not be present to drive the doors in the open direction it is desirable for a locking system for a passenger transit vehicle to be unlocked manually therein allowing for subsequent manual door movement toward an open direction.